2 – A True P6 Emerges
In this scenario the AAC tries to poach some Big 12 teams. At the same time so does the Mountain West. If each conference were able to get a few teams and then expand to 16 teams, there is a very real path for there to be a P6, even without the Big 12 existing.
Essentially in this model, the AAC would get West Virginia and two Texas schools to be in their conference while the Mountain West would get the Kansas schools, Oklahoma State, Iowa State and the remaining Texas team.
This would be the one scenario that would likely see BYU Football be unaffected in really any way.
Likelihood of happening: Unlikely
The problem with this scenario is that it is unlikely that none of the remaining Big 12 teams will not find a P5 home under the current system. If even two or three left for the ACC or Pac 12 it would make it very hard to have two P5 conferences emerge, although still very likely for one.